This invention relates to image forming screens for optical equipment, and more particularly to such a screen in which the image brightness is greatly enhanced uniformly over the surface of a plastic screen having a Fresnel lens thereon.
In my U.S. Pat. No. 4,339,188 an image forming viewing screen consisting of a ground glass viewing screen coated with an optical grade of epoxy bonding material is mounted in abutting contact with a Fresnel lens to obtain a very bright image. The rings of the Fresnel lens were disposed in abutting relationship with the coated surface of the screen. Due to space or other limitations in cameras such as single lens reflex cameras, and other optical devices where a two component system would be too thick or a glass focusing screen may be impractical, it is sometimes necessary to use an optical grade of synthetic plastic cast as a Fresnel lens integrally with the image forming screen on the opposite surface. The image brightness of such a screen is however poor in low light situations and it was not believed at the time I developed the subject matter of my aforesaid United States Patent that the brightness of a Fresnel lens-image forming surface combination itself could be increased.